Reproductive Effort and CO2 Dynamics of Wild Strawberry Populations

Reproductive effort including metabolic costs (REmet) was calculated for two wild strawberries, Fragaria virginiana and F. vesca. Five populations were studies for 2 or 3 yr each on sites comprising stages in succession near Ithaca, New York. Field and laboratory studies of biomass, environment, and CO2 exchange characteristics wee integrated using a model of whole—plant carbon dynamics. Leaves supplied 96—99% of total yearly plant photosynthesis; reproductive structures also had some photosynthetic capacity. Results of the model suggest that photosynthetic carbon gain is the major factor limiting growth. Sexual REmet decreased from 12% in an open, recently disturbed habitat to 4% in a shady forested site, while vegetative REmet decreased from 29 to 9% over the same series of habitats. Initial capital, harvest time, and the ratios of respiration costs to costs of new structures in different habitats all contributed to variation in calculated reproductive effort based on different definitions. Variation in REmet among sites and among years on the same site suggest substantial control of reproductive effort by environmental conditions within some genetically determined limit.